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Plant Growth And Development (Plant Hormones (Gibberellins (Produced in…
Plant Growth And Development
Plant Hormones
Auxins
Those produced by apical meristem create apical dominance where plant growth is upward: removing auxin causes it to grow sideways.
Low auxin concentration stimulates cell elongation, higher concentrations has a reverse effect.
Cytokinins
Promote cell division by stimulating protein production needed for mitosis and cytokinesis.
Gibberellins
Produced in apical meristem, transported in vascular tissue.
Stimulate plant growth by changing its cell wall, stop dormancy in seeds and reverse genetic dwarfism.
Promote the growth of taller, stronger and early flowering plants.
Ethylene
In the tissue of ripening fruits, drying leaves and flowers.
Weakens the cell of unripe fruit breaking down complex carbohydrates.
Abiscic Acid
Synthesized in mature leaves, fruits and root caps, inhibits growth.
Blocks the carbon dioxide intake by controlling leaf stomata opening and closing.
Response To Environment Stimuli
Nastic
A plant's response to stimulus not associated with stimulus direction.
Example: flower petal opening at day, closing at night to conserve heat.
Tropic
Tropism
Growth response of a plant to external stimulus: if it grows towards, its positive, if its growing away from stimulus it's negative.
Phototropism
Growth response to light from unequal auxin distribution.
Cells on the side away from light elongate, causing the stem to grow larger, bending to the direction of light.
Gravitropism
Growth response to gravity: roots = normally positive.
Negative = when stem grows upward pushing against gravity for maximum exposure to light.
Thigmotropism
Growth response to mechanical stimuli through contact.
Nutrients
Macronutrients include nitrogen, potassium, calcium, magnesium, phosphorus and sulfur.
Micronutrients include chlorine, iron, manganese, boron, zinc, copper and molybdenum.
Soil pH
Most plants thrive in slightly acidic soil ranging from 6-7 (pine, spruce, magnolia, holly, potatoes).
Some tolerate basic soil from 7-8 (geraniums, petunias, beans, lettuce, pears)